subtests.docker_cli: Add run_env test

This test contains workaround using InteractiveAsyncDockerCmd due of https://bugzilla.redhat.com/show_bug.cgi?id=1131592 and it fixes the issue https://github.com/autotest/autotest-docker/issues/252

this tests the ENV related features. Currently it only contains one
subsubtest, which is focused on linked containers. It sends data
using the addr from ENV to the server, which resends them back.

In the end it checks the valid data + ENV variables added via `-e x=y`
including the linked values ($linked_ENV_...)

Signed-off-by: Lukáš Doktor <ldoktor@redhat.com>
This is okay  for now, but next time try and stick with reliable features that "work" today.  We have no idea if/when any bug will be fixed, so they can end up holding tests "hostage" for quite a while.  We have other tests that do "interactive" stuff w/o trlying on workarounds. Just copy from them, no need to re-invent the wheel each time.